Telephone system



Jan. 23, 1934. R. F. STEHLIK 1,944,698

TELEPHONE SYSTEM Filed Sept. 28, 1931 3 Sheets-Sheet l Ruin FR Frank E'Ehlik m Jan. 23, 1934. R STEHUK 1,944,698

TELEPHONE SYSTEM Filed Sept. 28, 1931 3 Sheets-Sheet 2 CAL kw HLIdD-EFI'L Frank Etahlik Jan. 23, 1934. R F STEHLIK 1,944,698

TELEPHONE SYSTEM Filed Sept. 28, 1931 3 Sheets-Sheet 3 -I1TUE1F HudElF h Frank ETEhHk Patented Jan. 23, 1934 UNITED STATES TELEPHONE SYSTEM Rudolph Frank Stehlik,

Chicago, Ill., assignor to Associated Telephone and Telegraph Company, Chicago, Ill., a corporation of Delaware Application September 28,

1931, Serial No.

565,440, and in Great Britain October 1, 1930 Claims.

The present invention relates to telephone systems and is more particularly concerned with small private branch exchanges. Such private branch exchanges may be installed in ofi'ices 5 where there is a private automatic exchange installation and in this event the subscribers may be provided with instruments having access both to the private automatic exchange lines and to the private branch exchange.

The invention more particularly concerns the provision of special arrangements at the operators position at the private branch exchange but it will be understood that certain of these arrangements are not limited to offices fitted also 15. with private automatic exchanges.

The chief object of the invention is the provision of new and useful operating features together with improved circuit arrangements to facilitate easy maintenance and operation.

According to one feature of the invention the calling lamp from the trunk exchange cannot be extinguished by simply inserting a plug in the associated jack but in addition the operator must operate her trunk listening key. This feature has the advantage that it prevents the operator from plugging up a number of trunk calls at the same time and answering them at her leisure.

According to another feature of the invention provision is made for the operator to listen to either the trunk or the local line by the operation of a single key in either of two directions the circuits being separated during this operation so as to prevent overbearing.

The invention will be better understood by referring to the following description of various embodiments of the invention taken in conjunc tion with the accompanying drawings comprising Figs. 1, 2 and 3.

Fig. 1 shows a cord circuit and associated apparatus for use in setting up connections between local lines and trunk lines leading to a public exchange and is particularly for use in combination with a private automatic exchange by means of which the various local lines may be connected together. Subscribers to be provided with facilities for making calls to the public exchange over the private branch exchange are provided With two-button instrument sets which are arranged so that by operation of the appropriate button the handset can be connected either to a line leading to the private automatic exchange automatic exchange only. The operators set is arranged somewhat differently and is provided with a key OK which in its normal position connects the operators telephone (which is connected across the lead OT) to the private branch 6% exchange, and in its operated position connects the operators telephone to the leads OAL which forms a regular line on the private automatic exchange. a L a On an incomingcall, ringing current is received over the line TL from the main exchange which, passing through the'condenser 64 and the right hand winding of relay L, causes relay L to operate and lock up over its left-hand winding and contacts 59 and 60 at the same time at contact (0. 58 closing a circuit for the trunk call lamp' TS in series with the pilot relay PR. and at contact 57 connecting earth to relay CO. The trunk call lamp TS thereupon glows to attract the attention of the operator who then inserts the plug TP into the jack TJ. This, however, has no immediate effect. She then operatesthe talking key to operate the springs TK which at contact 28 complete a circuit for relay T, at contacts 27 and 29 connect relay A to the leads OT across which the operators telephone is bridged, at contact 25 open a point in a bridge circuit across the speaking conductors, and at contacts 26 and 30 disconnect the local plug LP from across the terminals of relay A.

Relay A and relay T both energize; relay T at its contact 53 connects battery through resistance 54 over the sleeve of the plug TP to, relay CO, which'energizes and at contacts 60 and 61 opens the locking circuit and initial energizing circuit for relay L. Relay L releases, at contact 58 opens the circuit of the calling lamp TS and at contact 56 connects battery in place of earth to the lower terminal of relay CO which thereupon releases. Relay T also completes a circuit for relay C at contact 52 and for relay S at contact 51.-- Relay C locks up over contacts 34 and 48 independently of contact 52 of relay T while relay S locks up over contacts 39 and 47. Due to the operation of relays A- and C, the upper winding of relay H is bridged across the main exchange line over contacts 32 and 46 toeiiect the operation of a battery feed relay at the main exchange, re

lay H also operates in this-circuit. Relay'C. at 05 9 contacts 46 and 50 completes a circuit from the trunk line to the speaking condensers to enable the operator to converse with the calling party; and ascertain the name or'number of the want-' ed party.-'

It will be noticed that the operator cannot extinguish the lamp TS by simply inserting the plug TP but she has also to operate the listening key. This arrangement prevents the operator plugging up a number of trunk calls and answering them at her leisure.

The operator then inserts the plug P into the jack of the wanted party, say the jack LJ, and

depresses the ringing button RK intermittently to connect up a source or" ringing current at contacts l4 and 17 to ring the wanted subscribers bell. During the ringing operation the operator switches over the talking key to release the springs TK and operate the springs LK. Relay A is again energized in series with the operators telephone when the springs LK are operated and any momentary release of relay A due to the change-over operation is without effeet-as relay C isslow to release. Immediately the springs TK restore, contact 25 connects the upper winding of relay H in bridge of the main exchange line dependent upon contact 38 of relay S, so that relay H and the battery feed relay at the main exchange will be maintained operated.

The operator upon hearing the called subscriber reply, informs him of the main exchange call and if the called subscriber accepts the call the operator restores the talking key to the middle position. Relay A remains operated over a circuit including the called loop and contacts 26, 15, 16 and 30. V

If the called subscriber wishes to recall the operator he dials the digit 0 or any large digit,

relay A thereupon releases intermittently and causes the supervisory lamp SL to flash overthe following circuit: battery, relay PR, lamp SL, contacts .37, 33, 47, earth. This operation 'may be continued until the operator answers.

The operator may listen and speak either on the trunk line or the local line by operating the springs TK or the springs LK, as the case may be, and it will be noted that the speaking connection between the two lines (which is shown in thick lines) is broken when either set of springs is operated. Talking battery is fed to the called party from relay A.

When the subscriber replaces his handset, relay A releases and is followed by the relay C,

1- and the release of relay C causes the release of relay S. Relay S upon releasing opens the circult of relay H and the battery feed relay at the main exchange whereupon these relays release. The supervisory lamp SL glows to attract the attention of the operator over the following circuit: battery, relay PR, lamp SL, contacts 36, 44, 40, 19, sleeve of plug LP and jack L5, earth.

If a subscriber having access to both the private automatic exchange and the private branch exchange wishes to extend a connection to the main exchange he operates the trunk button of his telephone set, whereby his telephone is connected to his line jack on the manual board. The line lamp LS associated with that jack thereupon glows to attract the attention of the operator. The operator then plugs the local plug LPinto the jack LJ and operates the springs LK to ascertain the requirements of the calling subscriber.- The operator then inserts the trunk plug TP into an idle trunk jack and restores the ing to the public exchange. Relay A operates overthe calling loop. Relay II operates in the following circuit: earth, contacts as and 49,.re-

lay H, contact 24, sleeve of plug TP and jack TJ, relay 00, contact 56, resistance 55, battery. At contact 45 it closes an operating circuit for relay C which at contact 49 opens the initial energizing circuit of relay H, at contact 48 closes a locking circuit for itself, and at contact 46 connects the upper winding over relay H across the conductors of the trunk. Relay H is held energized by battery fed from a line relay at the main exchange. Relay CO does not operate in series with the lower winding of relay H. The calling subscriber upon receiving dial tone from the main exchange can set up the connection by dialing, relay A repeats the impulses by interrupting the loop circuit including the upper winding of relay H at contact 32. On the first impulse relay I operates over contacts 33 and t7, at contact 41 short-circuits its upper winding so that it remains operated throughout the impulse train, short-circuits the upper winding of relay H at contact 2 to cut out its impedance from the iinpulsing circuit, and at contact 43 connects up earth to operate relay CO and thus to prevent an incoming call from operating relay L while an outgoing call is being set up.

When a subscriber has been connected to a trunk leading to the public exchange he may make as many calls as he desires by hanging up for a moment of time sufficient to allow the automatic switches at the main exchange to release after each call, Without requiring any operation on the part of thejoperator. When he finally restores his handset the operator will observe the lamp SL glowing continuously and will thereupon remove the plugs from the jacks. If, how ever, during the interval between the termination or a call and before the removal of the plugs a call should be received from the main exchange, the trunk call lamp TS will glow and relay L will substitute earth in place of battery connected to relay CO so that the local subscriber cannot interfere with the incoming call. The operator will then answer the incoming call in the usual way and if the call is for the local subscriber already connected she will simply operate the necessary keys. If, however, the call is' for another subscriber she will transfer the local plug to the jack of that subscriber and'ring in the usual way. It will be seen, therefore, that except for the fact that the plugs are already inserted in their jacks, the call is treated in the same way as a normal call.

In certain telephone networks, the toll operator rings on a line even though it is busy and the 130 circuit arrangements shown are suitablefor use in such a network in which case the relay L will operate when a toll operator rings on the line and will cause the lamp TS to glow. As already explained this lamp can only be extinguished by 135 the operator at the private exchange plugging in and operating the talking key.

The operator is provided with a telephone set connected to: the line OT and with a local line GAL extending to the private automatic ex- 140 change. A relay. OR bridged across this line operates when a subscriber connected to the private, automatic exchange calls the operators number, and thereupon locks up over contacts 'll and 69 and lights the operators local line call 145 lamp OL at contact '22. The operator will then operate the local line key OK and communicate with the calling subscriber.

In order to provide easy interconnection for nishtse vio e chl e ro t m n n e 0 passes through a break jack NJ so that each of these lines can be readily connected to a local line by means of a straight-through cord with two plugs. Relay PR is arranged to operate whenever a circuit is completed for any of the lamps so that, when the key AK is operated, a circuit will be completed for the alarm AL to attract attention when the operator is away from the board.

Fig. 2 shows a cord circuit which is similar to that shown in Fig. 1, but has in addition two relays M and N associated with the local plug LP. This arrangement is intended for use with a private automatic exchange in which the subscribers instrument sets are connected only to a single line which is connected to the private automatic exchange through a break jack on the private branch exchange. Certain subscribers are provided with a lamp LS terminating the lead (1 and are enabled to control the lighting of this lamp to signal the operator. Only these subscribers can be connected to the public exchange. The lines of the remaining subscribers do not pass through the manual board but are directly connected to the private automatic exchange. As in Fig. 1 the operator is connected to the private automatic exchange over a regular line, which, however, will not pass through a break jack.

The operations for an incoming call are similar to those just described except that as the Wanted subscriber has only a single line with a condenser and bell it is necessary for the operator to test whether the line is idle before applying the plug.

' To do this the operator actuates the springs vLK and applies the tip of the plug LP to the sleeve of the jack LJ. If the line is idle no effect is produced but if the line is busy, earth potential connected to the sleeve of the jack over lead 0 from the private automatic exchange will cause the condenser 74 connected to the upper winding of relay A to charge, and a click will be produced in the operators receiver, the intensity of this click is reduced by battery connected through resistance 75.

If the incoming call is a toll call the operator will plug into the jack LJ irrespective of whether the line is idle or busy. The action of plugging into the jack disconnects the subscribers line from the private automatic exchange and connects it to the cord circuit. If the line is idle, the operator will momentarily depress the ringing button RK at intervals and in one of the intervals will operate the talking key to actuate the springs LK. When the operator plugs into an idle line relay M operates in series with battery connected to the sleeves of the jack over lead 0 through the line relay of the wanted subscriber. In the case where the operator extends a toll call to a busy line, the operation of relay M takes place when the local connection is released. Relay M upon operating at contact '76 closes a circuit for the upper winding of relay M which in turn operates, at contact 77 marks the called line busy by connecting earth through its low resistance lower winding, at contact 78 shortcircuits the busy test condenser 74, and at contact '79 closes a point in the circuit in which the supervisory lamp SL lights upon the release of the connection.

In the case or" an outgoing call the calling subscriber by dialing a special digit operates the private automatic exchange to cause the calling lamp LS to light, the operator thereupon inserts the local plug LP into the associated jack LJ,

whereby the calling subscribers line is disconnected from the private automatic exchange. Due to the disconnection of the private automatic exchange, the earth connected to the sleeve of the jack LJ over lead 0 is replaced by battery whereupon relays M and N operate in the manner previously described. and the outgoing call is extended in the manner described in connection with Fig. 1.

Fig. 3 shows a similar cord circuit but ar-' ranged so that the operator can set up connections manually between the local subscribers and can also extend calls to and from the public exchange. This arrangement is particularly for use where the local subscribers are not provided with dial switches, and in this case, since all the outgoing calls to the public exchange can be set up by the operator who will be provided with a dial switch, the subscribers instrument sets are each connected by a single line to line jacks on the manual board.

The cord circuit is modified by the addition of a ringing key RKl associated with the trunk plug TP, a supervisory lamp SL1, and relays P and Q.

In the case of calls to and from the public exchange, the operations which take place are similar to those previously described, since in calls to the public exchange relay Q is not connected up at contact 80 whilst in calls from the public exchange it does not receive sufficient current in series with the winding of relay CO. The lamp SL1 is not required in this type of connection but connected in parallel with the lamp SL at contact 81. It will be noted that if the talking key is left thrown to actuate the springs LK when a connection has been set up the lamp SL will be lighted in a circuit extending over contact 82 and the sleeve of the plug LP and thus indicates to the operator that the speaking connection is not complete.

When the calling subscriber wishes to be connected to another subscriber the operator inserts the trunk plug T1? in the jack-of the call-- ing line and momentarily presses the associated ringing button RKl, during an interval in the 1120 ringing operation she operates the trunk key to actuate springs TK whereupon relays T, C and S operate as described with reference to Fig. 1. Since, however, the sleeve of the local jack is not connected to battery but to direct earth, re- I lay H will not operate but instead relay Q will operate over its upper winding and contact 80 and will lock operated over its lower'winding and contact 83. Relay Q at contact 84 completes a circuit for the lamp SL1 in a circuit including a contact 85 of relay P and the sleeve ofthe plug LP, at contact 86 disconnects relay H from the speaking conductors and at contacts 87 and 88 connects up relay P to supply speaking current to the called subscriber. Relay P operates when the called subscriber replies, at contact 85 opens the circuit of the lamp SL1 and at contact 89 closes a holding circuit for relay C. When both subscribers restore their handsets, the battery feed relays A and P release and are followed 40 by relays C, S and Q whereupon the lamps SL and SL1 glow to indicate that the plugs can be removed. i What I claim as new and desire to secure by Letters Patent is: 1 1. In a telephone system, a manual board, a plurality of incoming lines each terminating in a jack at said board, a signal associated with each line, a plug ending cord circuit including a listening key, means responsive to a call re- 1550 responsive to an incoming call, and means jointly controlled by the connection of a cord circuit to the calling line and the operation of said listening key for restoring said signal.

3. In a telephone system, a manual board, a plurality of lines each terminating in a jacket said board, a signal associated with each line operated responsive to a call received over the line, a cord circuit having an answering plug and a listening key, and means for restoring an operated signal only responsive to the insertion of said plug into the jack of the calling line and the operation of said listening key.

4. In a telephone system, a manual board, a plurality of lines each terminatin a jack. at said board, a signal associated with each line operated responsive to a call received over the line, a cord circuit having an answering plug and a listening key, means for restorin an operated signal responsive only to the insertion of said plug into the jack of the calling line and the operation of said listeningkey, and means responsive to the operation of said k y for preparing said signal for operation responsive to a-subsequent call over the line. v

5. In a telephone system in which connections are-extended by manually operable cord circuits at a manual board, a key associated with each cord circuit, a plurality of incoming lines, signal associated With each line and operated responsive to. a call over the line, means jointly controlled by the connection of a cord circuit to a calling line and the operation of the associated key for re storing the calling line signal, and other means controlled by said key for preparing the signal to respond to a subsequent call received over the line.

6. In a telephone s'ysteni, an operators position having a cord circuit thereat, a plurality of local subscribers lines, an operators line, a batteryfeed relay in said cord circuit for feeding talking battery to said local lines, and means for controlling said relay over a connected local line and over said operators line.

'7. In a telephone system, an operators posiion, a cord circuit having two capaoitively coupled sections, a plurality of local subscribers lines, a line extending from the operators telephone circuit, a battery feed relay in-the section of said cord circuit which is connected with the local lines in extending connections, said relay supplying talking battery to a connected local line, and means for controlling said relay over a connected local line and over said operators line. a

8. In a telephone system, a plurality of subscribers lines and a plurality of trunk lines, a cord circuit for interconnecting said lines and trunk lines to complete both local and trunk calls, said cord comprising two sections coupled by condensers, means for connecting talking battery to one section of cord both on local and trunk calls, and means for connecting talking battery to the other section of said cord only on local calls.

9. In a telephone system, a plurality of local subscribers lines, a plurality of trunk lines, a cord circuit for interconnecting said lines to complete both local and trunk calls, a line extending from an operators telephone circuit, and a relay in cord circuit for supplying talking battery to local subscribers lines and to said operators line and controlled over both.

10. In a telephone system, a manual board, a plurality of local lines and a plurality of trunk *rninating at said board, a cord circuit for inter connecting said lines, a listening key in said cord circuit, a relay, means responsive to the operation of said key for initially operating said means under the control of one of the connected lines for maintaining said relay operated,

and contacts on said relay for completing a talking connection through said cord circuit. RUDOLPH FRANK STEHLIK. 

